A wide variety of pneumatic, hydraulic, and electric driven impact tools are used throughout manufacturing and construction. Most of these tools can trace their origins back to the invention of the jackhammer in the late 1800's and operate under the principle of storing energy via a compressed gas or utilizing a pressurized fluid, then releasing the stored energy to perform useful work. Common tools include jackhammers, pneumatic impact wrenches, pneumatic rock drills, post drivers, nail guns, and pile driving equipment. Due to the structural requirements of utilizing high pressure fluids or large volumes of compressed air, these tools are generally heavy, bulky, relatively expensive, and require large quantities of energy to operate.
Hydraulic breakers of various sizes work on the principle of moving a piston against a reactive force (commonly provided by a spring) and then releasing the piston to facilitate an impact. With this design, oil or other fluids may be used to stroke a hydraulic cylinder which is incorporated as part of the piston. The hydraulic fluid lifts the piston thereby compressing a gaseous spring. The oil is then released, and the piston is propelled to an impact. A drawback of this design is that a valve must be actuated and the oil evacuated with each stroke or impact of the piston, resulting in a parasitic load that consumes a portion of the stored energy and reduces the efficiency of the jackhammer. Additionally, as the piston nears the end of its stroke, it is decelerated as the oil cushions the movement and the valve begins to actuate for the next lift cycle, thus diminishing the impact of the piston. To counter these losses, higher reactive forces or hydraulic pressures may be used, which requires greater energy input, structurally stronger equipment, and increased maintenance, thereby resulting in a shorter tool life.
Electric breakers and gasoline-powered breakers (petrol breakers) work on the reciprocating principle. A cylinder is moved up and down rapidly by means of a crankshaft and rod. A snug fitting piston is placed inside the cylinder and as the cylinder is moved upward, a vacuum is created that lifts the piston. As the cylinder is then forced downward via the crankshaft and rod, the piston is forced downward as well. Once the cylinder passes half stroke (the point of maximum acceleration), it begins to slow. The piston continues in a free body motion until the point of impact. Once the cylinder begins to slow, the piston is no longer accelerated, resulting in a limited impact force.
Pneumatic hammers of all sizes employ a piston within a cylinder. A pulse of compressed air pushes the piston upward until the piston contacts a valve. The valve then opens, allowing a large pulse of compressed air to accelerate the piston downward producing an impact on a work tool. One drawback of pneumatic hammers is the requirement for large quantities of compressed air, which requires energy intensive compressors. A second drawback of pneumatic hammers is the noise pollution associated with releasing compressed air and the running of large compressors.